1. Field of the Invention
The present invention relates to a motor drive device, an image reading device, an image forming apparatus, and a motor drive method, and particularly, to a motor stopping control.
2. Description of the Related Art
It is well-known that it is typical for stepping motors to be employed as drive devices when an image reading device such as a scanner drives an image sensor unit and reads in an original document. A stepping motor is capable of controlling rotational speed using a number of excitation modes. However, when stopping positions in two excitation modes do not match while rotation of the stepping motor changes from one excitation mode to another excitation mode, the position of the rotor becomes indeterminate and images that are read in can become distorted.
In order to resolve such problems, such a motor drive device that smoothly makes a transition between two excitation modes during driving has been disclosed in Japanese Patent Application Laid-open No. 2004-140890. This motor drive device ensures that the position of the rotor does not become indeterminate in the transition to the next excitation mode. This is achieved by determining, during transition from one excitation mode to another excitation mode, that the rotor moves to a position common to the two excitation modes, and then making a transition.
However, with the technology disclosed in patent document 1, when temporarily stopping the stepping motor and starting operation in an excitation mode different to the excitation mode during stopping, the operation of the rotor becomes indeterminate and distortion of read images occurs when the rotor is not stopped at a position corresponding to the excitation mode operation is to start for.